Motors or actuator within which a terbium/iron alloy (known as Terfenol) exhibits large magnetostrictive effects in the presence of a magnetic field, are generally well known in the art. An actuator device embodying a Terfenol rod that is magnetostrictively deformed in length by magnetic field pulsations applied through a surrounding coil, is disclosed for example in U.S. Pat. No. 5,231,887 to Arvidsson et al. A magnetostrictive type of motor system having a unidirectionally driven rotor is disclosed in U.S. Pat. No. 5,341,056 to Maccabee, wherein plural Terfenol rods with activating magnetic coils are utilized. Some of such rods are magnetostrictively deformed into engagement with the rotor, intermittently, while being continuously engaged with other of such rods, all of which are also engaged with a reaction frame. U.S. Pat. No. 5,357,232 to Suzuki et al. is of interest in disclosing a magnetostrictive element having a Terfenol rod coaxially positioned within a hollow magnet to which it is coupled by a soft magnetic yoke to form a closed magnetic circuit therewith. U.S. Pat. No. 5,382,863 to Tyren is also of interest in disclosing a Terfenol rod that is deformed in one direction by a magnetic field causing a magnetostrictive change.
It is an important object of the present invention to provide a magnetostrictive type of motor system capable of operation under a wide range of speed and torque by control of an alternating electrical input so as to accommodate many different loading applications, including for example applications requiring a high start-up torque.
Additional objects of the invention in accordance with the foregoing object is to provide a magnetostrictive motor system capable of rapid delivery of high torques to a load as well as to accommodate lower load requirements without drive ratio control of gearing or the like.
Other objects include the provision of a magnetostrictive motor that is readily adjusted, and has simple repair, maintenance and check-up capabilities.